With communicating data through the Internet, there is a problem of preventing spoofing of a sender.
There has been proposed a known verification technique using an electronic signature in order to prevent the spoofing of the sender. For example, a known art proposes verification of the electronic signature. The known art verifies the electronic signature, which is included in a device certificate attached to electronic mail, using a certification authority certificate issued by a certification authority for authenticating the device certificate. The known art specifies an act of the spoofing of the sender by determining whether or not the device certificate is issued by the certification authority.
A first known art proposes an Internet FAX that adds a verification result and prints electronic mail if verification of an electronic signature is succeeded. A second known art proposes an Internet FAX that prints electronic mail even if verification of an electronic signature is failed.